Why paint it black?

Hello.
I’ve been getting one can of sweet red bean soup a day from the vending machine at work.
This year we had a longer warm season, so replacing the drinks in the vending machine has been delayed and I was worried that the vending machines might not have hot sweet red bean soup this year. But, I am so glad that I can drink it again this year.

And now, I would like to talk about why the inside of the control cavity is all black.
There are many guitars and basses that are not painted black, but recently, guitars and basses in the price range of 50,000 yen are even painted black. I think many people might be curious as to why this is so I’m going to talk more about this further.

Well.
As it turns out, the black part is conductive paint. Its purpose is to reduce noise in the cavity.

The reason is the same as for applying aluminum sheets, which I wrote about in my last blog, only the method and the tools used are different.
In other words, conductive paint is a liquid version of an aluminum sheet.
More precisely, well, you can say that they are different, but... the purpose is the same, so here is a very simple and easy-to-understand explanation.

“Oh, I see. My guitar has conductive paint on it so it makes less noise.”
This is not the case with conductive paint.

Why is that? Well, let me give you 2 explanations.

1. There is a possibility that the paint is not properly grounded.
This is the same as I explained on the aluminum sheet from my previous article, but even if conductive paint is applied, if it is not grounded, it will absolutely cause and increase the guitar noises.
The control cavity may be safe because there are pots and other parts, but if the paint is applied to the pickup counterbore, there is no place around the painted parts to reduce guitar noise, so it must be grounded using a lug or something similar.

Montreux / Lug Set

By the way, this item is the lug.
You can connect the ground wire to the designated point inside the control cavity.

2. Conductive paint is not being applied properly.
Although conductive paint is applied on many relatively inexpensive models, as shown in the photo, the paint may be applied unevenly and not fulfill its intended function.

For example, if the conductive paint is too thin, its effect will be reduced and there will be no conductivity.
Therefore, it is important to make sure that the conductive paint is uniformly applied at a constant density.

Well, this explanation is probably not giving you a good impression of conductive paints, right?
No, no, no, it can be a very good thing if used correctly.
It is so effective that many guitar makers use it, and more than 90% of the so-called high-end guitars in the higher price range use it. (This is my experience, so I have no concrete numbers, evidence, or sources.)

Now that I have given an explanation about conductive paints, I will now talk about the different types of conductive paints.

First, there are two types of conductive paints: water-based and oil-based.
The difference between the two is that water-based paint is diluted with water, while oil-based paint is diluted with paint thinner.
This may sound obvious, but it’s important to note this.

Some guitars have a lacquer coating that dissolves with paint thinner.
That is to say, if you use oil-based conductive paint on a lacquered guitar, the paint inside the cavity will start to dissolve, and if you accidentally get paint on the body, your precious guitar will be ruined...
Therefore, water-based paint has to be used for lacquered guitars.

Huh? If there is a possibility of such a thing happening, you might think that it would be better to use water-based paint regardless of the type of paint, but things aren’t that simple.

There are advantages and disadvantages to both types of paint.

First of all, as I mentioned earlier, water-based paint has the advantage of being used for lacquer coating, but its disadvantage is it’s very difficult to get a thick enough coating with it.
This is because the paint itself does not have too much viscosity because it is diluted with water.
Also, because this type of paint is thinned out with water, it dries very slowly, so it takes longer to apply a single coating of paint.
The next point is the most important.
When applying water-based paint, depending on the material that it’s being applied to, it may repel quite a bit.
You can see this when you actually apply the paint, but it is much more repellent than you would think.
However, there is a countermeasure to this problem: sand down the area that you’re planning to paint with sandpaper in order to create a rougher surface and it will be much easier to paint.
No matter what you do, a little extra effort will go a long way for this type of project.

And then, there is oil-based paint. Oil-based paint successfully overcomes the disadvantages of water-based paint.
The paint adheres better and is easier to apply, and its high viscosity makes it thicker and it dries more quickly.
Oil-based paint is many times easier to apply than water-based paint.
The disadvantages are that it’s not suitable for lacquer paint as I mentioned earlier and it smells quite bad because it’s mixed with paint thinner.
If oil-based paint is inhaled too much, it can make you sick, so it’s better to ventilate the room well or work outdoors when using it.

Freedom Custom Guitar Research / Noise Hell SP-D-01

Freedom Custom Guitar Research / Noise Hell SP-D-02

Finally, I would like to conclude this post by sharing with you a method on how to apply conductive paint inside the control cavity and using copper or aluminum tape to make contact with a panel covered with an aluminum sheet, which I talked about in my previous blog post.

First, place the copper tape where you plan to screw holes on the panel (The reason for placing the tape where the screw holes are is to prevent the panel from floating and making the conduction unstable.)

Next, apply conductive paint over the entire cavity.
At this time, apply the paint so that it thoroughly covers the copper tape.
If possible, apply 2 to 3 coats of conductive paint.
Only the top side of the copper tape is conductive, and if you do not cover the entire tape with the paint, the conductivity will be unstable.

*The entire cavity should be painted, but to better show you where to paint, I only painted near the copper tape.

Finally, the wiring in the cavity is soldered to the back of the volume pot using lugs. (In the photo, active pickups are used and are soldered to the side of the pot because the board is located at the back of the pot.)

This will firmly ground the noise element in the control cavity and reduce noise.

How was it?
This time, I talked about conductive paints and I tried to make it as easy to understand as possible, but I hope you can understand it the way I tried to explain it.

Also, I personally recommend using adhesive aluminum sheets for shielding to reduce noise in the cavity, rather than conductive paint.
The reason is that conductive paint is difficult to handle, so using a sheet is easier to work with. If you don’t like it, just feel free to take it off.
However, no matter which method you use, the most important thing to do is to ground it!
As long as this is done properly, you should be fine.

Thank you for reading my article to the end.
Come again to the Sound House Staff Blog!